Various forms of devices to control decent have been disclosed in the prior art. These devices include general structural and operational features of the present invention which heretofore have been provided.
One example of these previously known devices is disclosed in U.S. Pat. No. 287,491. This patent discloses a fire escape in which a rope is passed between clamping arms. The clamping arm is comprised of two pieces of wood. The two pieces of wood each have a flat inner surface and are fastened together at one end by means of a hinge. The outer sides of the free ends of the wood pieces are rounded so that they form a handle and may be gripped by the hand. The inner surfaces of the arms have two transverse grooves near the hinge in which a rope slides. A strap or belt is attached to the clamping arm. To use the fire escape, the belt is buckled on the person and a rope is attached to a firm structure. The rope is passed through the transverse groove in the clamping arm. The person may control his descent by clamping the two pieces of wood with his hand.
A problem with the above-described fire escape device is that it is difficult to control the rate of descent. Great pressure must be applied to the clamping arm in order to slow one's descent. In addition, the method of buckling the clamp to the body is awkward. Finally, there is no safety brake if the clamping arm should fail or if one does not have the strength to clamp the two pieces of wood.
U.S. Pat. No. 527,529 discloses a fire escape in which a rope passes through a clamp. The clamp has two parts that are hinged together. Both parts of the clamp are provided with half grooves. A rope is placed in the grooves and the two parts are closed together. A finger wheel is provided so that the two parts can be clamped together onto the rope. A second rope, in the form of a loop, is attached to the clamp which will hold the person during his descent. To use the device, the person tightens the finger wheel to slow his descent or loosens the finger wheel to speed his descent.
With this particular fire escape, it is difficult to control the rate of descent. One has to screw the finger wheel tighter to slow his descent while trying to hold on to the device while descending. In addition, there is no secondary mechanism to easily slow or stop the descent if one is unable to use the finger wheel.
U.S. Pat. No. 4,056,166 discloses a rope climbing device in which a person may control his descent. The device includes two plates that are attached to each other by a hinge. Each plate has a partial groove in the facing surfaces for engaging the rope. A screw-threaded bolt and nut assembly connects the two members. The members can be moved to or away from each other for varying the frictional engagement between the slide and the flexible member. A sling is attached to the device to hold a person. In addition, a hook is attached to the outer face of one of the members. The rope can be looped over the hook to help control the rate of descent.
This device is also difficult to control. Although it is supplied with a hook over which the user may loop the rope to better control his descent, since the hook is open, the rope can easily fall off the hook causing an uncontrolled descent.